Technical Field
This disclosure relates to medical instruments and methods and, more particularly, to systems and methods for improved visualization of internal anatomy in medical applications.
Description of the Related Art
Coronary artery bypass grafting (CABG) is a surgical procedure for revascularization of obstructed coronary arteries. In conventional surgery, the patient's sternum is opened, and the heart is fully exposed. However, minimally invasive (MI) bypass surgery is performed through small ports between the ribs. An important part of a CABG procedure is the removal of a vessel from the patient's body, which is then used to bypass one or more atherosclerotic narrowings in the coronary arteries. The vessel most commonly removed and used is an Internal Mammary Artery (IMA), which may include a Left IMA (LIMA) or Right IMA (RIMA), which are located in the thoracic cavity.
During MI cardiac bypass surgery direct access to these vessels is not available, and they are removed using long instruments inserted into ports through intercostal muscles in spaces between the ribs. During MI surgery, a surgical assistant can hold the endoscope, or it can be held using robotic guidance. In the case of robotic guidance, visual servoing can be used to move the robot to a specific location. Visual servoing consists of selecting a point on the endoscope image, with the robot moving in such a way that the point becomes located in the center of the image.
IMA takedown is usually the most time consuming part of the CABG procedure. IMA takedown usually takes between 45-60 minutes, and the success of a bypass procedure usually depends on the quality of the harvested vessel.
The main challenges during this stage of procedure include the following. Endoscope images are the only visualization method for this procedure, but the endoscope provides only a limited view of a small segment of a blood vessel. For MI, a surgeon works with elongated instruments inserted between the ribs reaching below the sternum area. This makes it difficult since the artery being harvested needs to be carefully isolated from surrounding tissue and side branches have to be cauterized.
A length of, e.g., the LIMA artery, has to be sufficient to reach the bypass location on the coronary artery. It is very difficult to estimate the length of the harvested vessel artery during MI procedures (as opposed to open surgery, where the length can be estimated since all areas are visible and accessible). As the LIMA is removed from the middle and inferior part of the chest, it tends to be more embedded in the tissue, slowing down isolation and making visualization of the artery and side branches even more challenging.
The combination of technical difficulties for artery isolation and the unknown length needed for bypass contributes to an extended procedure time, as the surgeon either isolates a much longer arterial segment than needed in the more challenging distal area, or isolates too short a segment, which requires returning later for continued isolation of the artery.
The IMA is usually embedded into the tissue at the chest wall. An endoscope view alone may not be sufficient to expose all of the IMA branches. A failure to close (e.g., cauterize or clip) the side branches of the IMA when removing it from the chest wall will cause leakage on the bypassed artery that may cause further injury.